Electronic paper (e-paper), or electronic ink, is display technology that has gained popularity. Unlike conventional backlit flat panel displays, which emit light, e-paper displays reflect light like ordinary paper, making it more comfortable to read. The e-paper surface can also have a wider viewing angle than conventional backlit displays.
Many e-paper technologies can hold static text and images indefinitely without continued use of electricity. The frontplane of the e-paper is the material, or film, that is used to hold the electrically charged pigments and typically incorporates tiny capsules or physical particles that are moved based on the applied electrical filed. The backplane is typically made with thin film transistors (TFTs) that drive the frontplane by the electrical field created on it to attract and distract the pigments. Supporting platform technology, such as a controller, drives the backplane to supply the necessary voltage difference and current based on the image that needs to be generated.
A display with an electrophoretic frontplane forms visible images by rearranging charged pigment particles using an applied electric field. A specific example of an electrophoretic display incorporates titanium dioxide (titania) particles approximately one micrometer in diameter dispersed in a hydrocarbon oil. A dark-colored dye is also added to the oil, along with surfactants and charging agents that cause the particles to take on an electric charge. This mixture is placed between two parallel, conductive plates separated by a gap of 10 to 100 micrometers. When a voltage is applied across the two plates, the particles migrate electrophoretically to the plate bearing the opposite charge from that on the particles. When the particles are located at the front (viewing) side of the display, it appears white, because light is scattered back to the viewer by the high-index titania particles. When the particles are located at the rear side of the display, it appears dark, because the incident light is absorbed by the colored dye. If the rear electrode is divided into a number of small picture elements (pixels), then an image can be formed by applying the appropriate voltage to each region of the display to create a pattern of reflecting and absorbing regions.
These electrically charged particles suspended in a colored oil inside tiny microcapsules. Each microcapsule contains positively charged white particles and negatively charged black particles suspended in a viscous fluid. Instead of microcapsules, microcups can also be used such as SiPix e-paper films.
In the bichromal frontplanes, microscopic plastic beads having two hemispheres with different colors are encapsulated in a pocket of oil. Positively or negatively charged hemispheres rotate freely within the plastic based on the electric field is applied on the e-paper so that negatively charged hemisphere face up with the positively charged electrode, and vice versa. As e-ink does not need to be refreshed like backlit technology, the image stays in place until the next electrical charge. In this way, the display can power down to zero, using less power overall than a display that constantly needs refreshing.
E-paper displays can incorporate active matrix, segmented, and/or passive matrix technologies for their backplanes. An active matrix display typically incorporates a backplane and can have a large array of pixels that each of them is controlled by a Thin Film Transistor (TFT) array. An example of a commercial electrophoretic display is the high-resolution active matrix display used in the Amazon Kindle e-readers. The display is constructed from an electrophoretic imaging film manufactured by E Ink Corporation. Glass is a common substrate that is used to embed these thin film transistors, as glass can withstand the high temperatures needed for the display manufacturing process. The recent development of organic thin film transistor (OTFT), which utilizes lower temperatures during fabrication, allows a plastic substrate to be used for the backplane. Using a plastic substrate for the background enhances the flexibility and durability of the e-paper display, such that flexible e-paper can be manufactured using plastic substrates and plastic electronics for the display backplane.
Retailers typically place items for sale on shelves and place shelf tags on the edge of the shelves to provide potential purchasers information about the items on the shelf Retailers have been seeking a technology for automatically changing the information displayed on the price tags placed on the edges of the shelves. Electronic Shelf Label (ESL) technology allows retailers to remotely change the prices of the items, with or without human intervention. However, implementing ESL with a label for every unique item is often impractical, due to high cost. According to the Food Marketing Institute, a typical grocery store has 38,718 different products on display at a given time, which means that thousands of ESL's per store are needed for the typical grocery to have an ESL for each item. Considering the high price of an individual ESL, ESL technology is not preferred by retailers, especially for low value items.
Accordingly, it is desirable to provide a low-cost, low power-consumption, and durable solution to allow retailers to display information on the shelf edge, and, optionally, automatically update such information.